Despite the appeal of peritoneal dialysis (PD) to patients, physicians, and providers, there is limited understanding of the mechanisms behind PD's low and diminishing utilization in the US. Patient and physician determinants of PD utilization have not adequately explained its declining trends, suggesting that nonmedical factors in the healthcare delivery system have contributed to PD's limited use. The availability of PD treatment services at dialysis facilities plays an important role in patient decision-making and is a necessary pre-condition of PD utilization. A declining proportion of facilities offer PD services, which may be due to financial incentives that favor the use of hemodialysis (HD) over PD. In 2011, Medicare implemented an end-stage renal disease (ESRD) bundled payment that modifies the financial incentive of dialysis treatments to induce greater supply and utilization of PD at dialysis facilities. Through a systematic program of research, the goal of this study is to evaluate the cascading effects of ESRD UU bundled payment on 1) dialysis facility practice patterns, 2) patient utilization, and 3) patient outcomes of PD. This will be accomplished by merging several years of administrative databases from the US Renal Data System and Medicare to assess changes in organizational and patient outcomes impacted by payment reform in the years preceding and immediately following implementation of ESRD bundled payment. This project has three specific aims. Aim 1 of this study will examine changes in dialysis facility UU provision of PD services and identify factors associated with changes in dialysis facility PD availability and program size. Building from this work, Aim 2 will assess the extent of and factors associated with changes in utilization of PD among incident dialysis patients, modality switches and changes in PD patient characteristics after ESRD bundled payment. Building from the work of the previous aims, Aim 3 will evaluate the comparative effectiveness of bundled payment and changes in HD and PD utilization on patient hospitalization and mortality. Results from the proposed work will inform CMS, dialysis providers, and ESRD patients on the organizational and clinical impacts of payment reform. Our approach is innovative because it examines a range of organizational as well as patient outcomes impacted by ESRD bundled payment, involves the use of several merged administrative databases to improve the quality of existing standalone data on dialysis facility practices, and employs relatively unused analytic methods to inform gaps in the evidence base and future refinements to dialysis practices and Medicare policy. The proposed research is significant because Medicare payment reform is a natural experiment that should be rigorously evaluated to determine its effectiveness in achieving Medicare's goals of aligning patient preferences and clinical appropriateness for PD, reducing costs, and improving care for a growing population of patients with ESRD.